I'm trying to create an xmas items shop. When I try to stack most of them in a vending machine it will only accept single items, for example tree decorations (certain items like festive doorway garland stacks fine). I've tried it with a stacking plugin (Stacks) and without, same result. Is this normal, and is there anything I can do about it?

StackModifier seems missing some items from that christmas stuff.

Merged post

Open StackModifier.json search for Misc and add missing items in the list. Reload and set stacksize in your Panel /stackmodifier.

Example
"Misc": {
"fogmachine": {
"ShortName": "fogmachine",
"ItemId": -1973785141,
"DisplayName": "Fogger-3000",
"Modified": 5,
"Disable": false
},
"xmas.decoration.lights": {
"ShortName": "xmas.decoration.lights",
"ItemId": 1723747470,
"DisplayName": "Tree Lights",
"Modified": 5,
"Disable": false
},

I'm using the Stacks plugin (not umod), it does have these items in the default config but it still doesn't work no matter what I set it as. I'll try some other stacking plugins just in case.

I think you can adapt this method to your plugin in file https://pastebin.com/8Cp2GjTg and https://pastebin.com/nCZMHGnz

Yes I already tried that, makes no difference unfortunately.